/*
 *  Copyright (c) WSO2 Inc. (http://www.wso2.org) All Rights Reserved.
 *
 *  WSO2 Inc. licenses this file to you under the Apache License,
 *  Version 2.0 (the "License"); you may not use this file except
 *  in compliance with the License.
 *  You may obtain a copy of the License at
 *
 *    http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing,
 * software distributed under the License is distributed on an
 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
 * KIND, either express or implied.  See the License for the
 * specific language governing permissions and limitations
 * under the License.
 */

package org.wso2.balana.xacml3;

import org.w3c.dom.NamedNodeMap;
import org.w3c.dom.Node;
import org.w3c.dom.NodeList;
import org.wso2.balana.*;
import org.wso2.balana.ctx.AttributeAssignment;
import org.wso2.balana.ctx.EvaluationCtx;
import org.wso2.balana.ctx.xacml2.Result;

import java.net.URI;
import java.util.ArrayList;
import java.util.List;
import java.util.Set;

/**
 * Represents ObligationExpressionType in the XACML 3.0 policy schema
 */
public class ObligationExpression extends AbstractObligation {

	/**
	 * <code>List</code> of <code>AttributeAssignmentExpression</code> that
	 * contains in <code>ObligationExpression</code>
	 * 
	 */
	private List<AttributeAssignmentExpression> expressions;

	/**
	 * Constructor that creates a new <code>ObligationExpression</code> based on
	 * the given elements.
	 * 
	 * @param fulfillOn
	 *            effect that will cause this obligation to be included in a
	 *            response
	 * @param expressions
	 *            <code>List</code> of
	 *            <code>AttributeAssignmentExpression</code>
	 * @param obligationId
	 *            Identifier that uniquely identify ObligationExpression element
	 */
	public ObligationExpression(int fulfillOn,
			List<AttributeAssignmentExpression> expressions, URI obligationId) {
		this.fulfillOn = fulfillOn;
		this.expressions = expressions;
		this.obligationId = obligationId;
	}

	/**
	 * creates a <code>ObligationExpression</code> based on its DOM node.
	 * 
	 * @param root
	 *            root the node to parse for the ObligationExpression
	 * @param metaData
	 *            meta-date associated with the policy
	 * @return a new <code>ObligationExpression</code> constructed by parsing
	 * @throws ParsingException
	 *             if the DOM node is invalid
	 */
	public static ObligationExpression getInstance(Node root,
			PolicyMetaData metaData) throws ParsingException {

		List<AttributeAssignmentExpression> expressions = new ArrayList<AttributeAssignmentExpression>();
		URI obligationId;
		int fulfillOn;
		String effect;

		// First check that we're really parsing an Attribute
		if (!root.getNodeName().equals("ObligationExpression")) {
			throw new ParsingException(
					"ObligationExpression object cannot be created "
							+ "with root node of type: " + root.getNodeName());
		}

		NamedNodeMap nodeAttributes = root.getAttributes();

		try {
			obligationId = new URI(nodeAttributes.getNamedItem("ObligationId")
					.getNodeValue());
		} catch (Exception e) {
			throw new ParsingException(
					"Error parsing required ObligationId in "
							+ "ObligationExpressionType", e);
		}

		try {
			effect = nodeAttributes.getNamedItem("FulfillOn").getNodeValue();
		} catch (Exception e) {
			throw new ParsingException("Error parsing required FulfillOn in "
					+ "ObligationExpressionType", e);
		}

		if ("Permit".equals(effect)) {
			fulfillOn = Result.DECISION_PERMIT;
		} else if ("Deny".equals(effect)) {
			fulfillOn = Result.DECISION_DENY;
		} else {
			throw new ParsingException("Invalid FulfillOn : " + effect);
		}

		NodeList children = root.getChildNodes();

		for (int i = 0; i < children.getLength(); i++) {
			Node child = children.item(i);
			if ("AttributeAssignmentExpression".equals(child.getNodeName())) {
				expressions.add(AttributeAssignmentExpression.getInstance(
						child, metaData));
			}
		}

		return new ObligationExpression(fulfillOn, expressions, obligationId);

	}

	@Override
	public ObligationResult evaluate(EvaluationCtx ctx) {
		List<AttributeAssignment> assignments = new ArrayList<AttributeAssignment>();
		for (AttributeAssignmentExpression expression : expressions) {
			Set<AttributeAssignment> assignmentSet = expression.evaluate(ctx);
			if (assignmentSet != null && assignmentSet.size() > 0) {
				assignments.addAll(assignmentSet);
			}
		}
		return new Obligation(assignments, obligationId);
	}


	public String encode() {
		return null;
	}

}
